[Stoves] A photo of a lab test from Ulaanbaatar

Wed Aug 28 06:28:27 CDT 2013

Crispim, thanks for sharing this.

This give us a clear idea  of how far we can go with instrumentation of
cook stoves analysis, and how to obtain real time data.

Cool. I will share it with our staff here at Ecofogão.

Rogerio

2013/8/27 Crispin Pemberton-Pigott <crispinpigott at gmail.com>

> Dear Friends****
>
> ** **
>
> I am circulating this as an into to the test methods applied in Mongolia
> (and other places). It is a pretty good example of what the main
> measurements look like.****
>
> ** **
>
> The photo is of one of the two computer screens which side by side. On the
> top left is the Digital Scale Capture Tool (DSC) available for $50 once off
> payment to Jeremy fuzzychaos at gmail.com (as a thank you).****
>
> ** **
>
> On the left of the DSC screen is the mass from the scale per 10 seconds.
> On the right is the (approx) calculated power in kW reported per minute.
> The data is saved to disk each 10 seconds. Multiple copies of the DSC can
> be run at the same time, one for each scale used.****
>
> ** **
>
> Below the numbers screen is the average kW plot so far in blue and the
> cumulative mass burned (also so far) curve in red.****
>
> ** **
>
> Below that is the mass change detected by the scale per 10 seconds. The
> value is shifted by the wind and moving fuel but overall as time passes,
> the precision is high, about 1 part in 5000. The burn rate (green line) can
> be seen to be declining towards zero as the fire burns out. ****
>
> ** **
>
> There are 4 gas readings. This is the minimum if you want PM from a fire.
> On the left is the CO2 level in the diluter. The other three are measured
> directly from the stack (or hood). The CO is the concentration in the
> chimney, in this case. The next CO2 is the CO2 in the chimney and is of
> course higher than the CO2 in the diluter. The ratio between them is the
> level of dilution, in this case it is 3.232:1. The PM measured in the
> diluter is multiplied by the number 3.232 to give the equivalent of the
> direct measure from the chimney (which might be too high to measure
> directly). The dilution is variable with the turn of a knob.****
>
> ** **
>
> The O2 on the right is the O2 in the chimney. ****
>
> ** **
>
> Notice that the total of the O2 and CO2 on the right does not add up to
> 20.945%, the O2 concentration in the ambient air. This is because there is
> H2 burning (from the fuel) and being turned into H2O. That H2O is not
> measured on this screen and as you don’t know what it is looking at this
> picture, you can’t tell if the equipment is working perfectly or not. Maybe
> it is a measurement error, maybe it is diluted by water vapour (which it
> is).****
>
> ** **
>
> The CO is very low at 18 ppm. The value for EA is about 1.67 and Lambda is
> therefore 2.67. ****
>
> ** **
>
> 2.67 x 18 ppm = 30. So the CO(EF) is 30 ppm, meaning that if there was no
> dilution by air, the CO cell would read 30 instead of 18.****
>
> ** **
>
> The CO/CO2 ratio is 18/(6.730 x 10,000) = 0.0002674 or 0.0266% (very
> good).****
>
> ** **
>
> The ‘modified combustion efficiency’ is ****
>
> ** **
>
> 6.73/(6.73+18/10,000) = 0.9997 = 99.97%****
>
> ** **
>
> The kW blue line for power is the running average from the beginning so
> the value 11kW refers to the whole test as a whole.****
>
> ** **
>
> The PM value will be multiplied again by Lambda (dilution) to get a
> PM2.5(EF) value. This is the rating that the stove gets. ****
>
> ** **
>
> Quick review:  PM reading x dilution in the diluter x dilution by excess
> air = emission factor value. This is later multiplied by the mass burned x
> the volume of gases produced by the fire based on the fuel analysis. The
> result is the mass of PM (and by the same method the CO and any other gas)
> emitted during the test.****
>
> ** **
>
> Because the data is collected in real time, the stove can be tuned to find
> the best operating parameters. Sections of the test can be analysed later
> to create a plot of how the heat transfer efficiency, for example, changes
> with power or fuel condition (etc).****
>
> ** **
>
> Best regards****
>
> Crispin****
>
> ** **
>
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